DESCRIPTION The long-term objectives of this application are to characterize the biological activities of prostate specific antigen (PSA)-generated parathyroid hormone-related protein (PTHrP) peptides on cultured prostatic and bone cells. The hypothesis to be tested is that prostatic cells express unique forms of PTHrP which are involved in autocrine/paracrine growth-regulatory processes in the prostate and at metastic bone sites. Specific Aim 1 is to produce PSA-generated PTHrp peptides synthetically (for small peptides) and recombinantly (for large peptides). Recombinant PTHrP 1-141 will be produced using a bacterial expression system. Recombinant PTHrP 1-141 will be cleaved with PSA and the resulting peptides will be purified by a combination of chromatographic procedures. Specific Aim 2 is to analyze the bioactivity of synthetic and recombinant PTHrP peptides on primary cultured human prostatic epithelial cells. Synthetic and recombinant peptides will be tested for their ability to stimulate growth and differentiation of cultured prostatic epithelial cells. Specific Aim 3 is to analyze the ability of synthetic and recombinant PTHrP peptides to stimulate growth and differentiation of primary cultured human prostatic stromal cells. Specific Aim 4 is to analyze the ability of synthetic and recombinant PTHrP peptides to induce the osteoblastic phenotype using cultured murine osteoblast-like cells and several markers of osteoblastic differentiation. Identification and characterization of autocrine or paracrine activities of PTHrP in the prostate will add to our understanding of the processes that regulate growth and differentiation of prostate and how these processes are involved in the development of hyperplasia or cancer. Knowledge of the role of PTHrP in the biology of prostatic metastases to bone will facilitate the development of therapeutic agents to control the metastic process, to inhibit osteoblastic lesions at metastic sites, and to reduce the risk of associated fractures and bone pain.